Lithium hydroxide is a known transesterification catalyst for making methacrylate ester monomers via reaction of methyl methacrylate (MMA) with specialty alcohols (for example, see U.S. Pat. No. 6,048,916, GB 1,094,998, U.S. Pat. No. 5,072,027, U.S. Pat. No. 4,916,255, U.S. Pat. No. 4,672,105, JP 2007055910A). Inhibitors are typically employed in these reactions to keep the monomers from polymerizing during processing. Inhibitors often include, among others, the methyl ether of hydroquinone (MeHQ) and/or phenothiazine (PTZ).
There is continued interest in developing inhibitor combinations which allow the transesterification process to proceed at higher rates while maintaining excellent long term monomer product stability.
When these transesterification reactions are complete, the catalyst is often removed via filtration procedures that include the addition of either some solid filtration agent (such as diatomaceous earth; in addition to above references, also see JP03109350A) or a hydrocarbon solvent (see JP3106847A) to aid in precipitation and/or removal of the precipitated lithium salts. These filtration agents and solvents, however, create more waste and increase disposal costs.
There also remains a need for a process to remove the lithium catalyst (i.e., lithium salt) without the addition of filtration agents or solvents.